In carousel based ALD applications, a small gap (e.g., a few mm) between the susceptor and injector is used for deposition uniformity. Minimum flatness and parallelism of both the susceptor and injector are important for processing uniform ALD films. Flatness of a large silicon carbide coated graphite susceptor during manufacturing is difficult to control because of gravity and warpage from purification and at least two high temperature silicon carbide coatings. Additionally, the properties of a graphite plate vary with the direction of slicing of a graphite billet.
Flatness of the susceptor can affect in-wafer uniformity of film thickness and resistivity. However, poor parallelism of susceptor wafer plane to pedestal plane gives rise to axial runout and wafer-in-batch non-uniformity. Flatness and parallelism can be minimized by controlling graphite substrate machining and fixturing during high temperature silicon carbide coatings. However, the yield and control is low because of the use of a high temperature process and can be difficulty to control.
Currently, current susceptor-motor assembly hardware runout specifications are hard to meet with low yield of usable susceptor-motor assembly hardware. Axial runout results from poor parallelism of pockets plane to bottom pedestal plane. Current carousel batch processing chambers may use gap camera to measure the outer diameter runout. When the susceptor axial runout is high, the wafers are not equidistant to the injector plane in the vertical direction and causes wafer to injector distances to vary during processing.
Therefore, there is a need in the art for apparatus and methods to provide increased parallelism of the susceptor to injector planes and/or minimizing runout of the susceptor.